There are more than 1 billion cars on earth. Cubesats are smaller than a car and can be distributed in an additional dimension (altitude). I think there is little risk of oversaturation currently.
Well, cars can park (and stay parked most of the time). Cars generally do not go offroad.
Also, cars do not go 8 km/s (30 Mm/h, 17k mph). That really compensates the actual satellite size. And a single debris can ruin your day at these speeds.
Cars spend most of their time at rest, don't travel at cosmic speeds, and when they collide, don't send tens of thousands of pieces of shrapnel flying around the world for months/decades.
Cars seem to have a lot in common actually: satellites are "at rest" most of the time, it just that this rest could be a hazard as some point; but a car parked badly, around a sharp turn or in the middle of the highway would be a hazard as well. Cars can collide too, they can leave debris, which can become dangerous themselves for other cars, or pollute the nature around from leaks, ...
The only reason I'd say cars are in a "better" situation is simply because we can clean up. We don't do it yet with satellites.
Other cars can steer around a badly stopped car. Satellites can't. A better analogy would be if once they entered their lane, cars would have to travel down it at their maximum speed, without being able to steer, or brake. Under those constraints, I, uh, wouldn't get into a car.
Cars are also not phased if they run over a loose bolt. The same can't be said for satellites.
> We don't do it yet with satellites.
Basic orbital mechanics indicates that we won't ever be able to clean up Kessler-syndrome space debris in a remotely-economical manner. There'd be too much of it, and it would travel at vastly disjoint orbits.
Satellites have propulsion and sometimes adjust orbit.
Maybe a bolt wont break your car, but a nail will flatten your tire.
And most of the time we don't clean much the highways: a lot of small debris end up here and there...
The problem is indeed that cleanup is expansive and not interesting when it's not such a big hazard, but after some time the sum of those small hazards become a big problem, and the sum of cleanups almost impossible.
